xktoxk is really cktoxk, which has been renamed by itself.  The program
copies the ck*.* files (in any given directory) into xk*.* files in the
current directory.  This allows an experimental version of C-Kermit to
coexist with the standard version.  The resulting xk*.* files must be moved
to their own directory and renamed back to ck*.* using the xktock program,
before they can be compiled.